IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 34

same time providing excellent performance characteristics and f lexible administration of virtual ser vers. For more details on z/VM, see “What is z/VM?” (below). Providing a secure virtual environment is more important than ever because increasing numbers of organizations and institutions worldwide are turning to virtualization to reduce IT costs. The virtualization layer is an attractive target that, if compromised, would provide easy access to all of the data used by all of the hosted virtual servers. Interpretive-Execution Facility The IBM System z* architecture provides the foundation for the functions the control program (CP) uses to maintain system integrity. At the core of its virtualization functions is the interpretive-execution facility that permits a virtual server instruction stream to run on the processor using a single instruction, Start Interpretive Execution (SIE). (For more information on SIE see “References,” page 38). This facility has been enhanced in each generation of the mainframe since its introduction on the IBM 308X series of processors in 1981. When CP runs a virtual server, details about the virtual server’s execution environment are provided to the hardware as input to the SIE instruction. The SIE instruction runs the virtual server until, for example, the server’s time slice has been consumed or the server wants to perform an operation that the hardware can’t virtualize on its own. At that point the SIE instruction ends and control is returned to CP, which simulates the instruction, performs I/O or simply places the virtual server in an involuntary wait state. Once the instruction has been handled, CP again schedules the virtual server to run and the cycle starts again. In this way, the full capabilities and speed of the CPU are available to the virtual server, and only those instructions that require CP assistance or validation are intercepted. CP uses these interceptions to impose constraints on the operations a virtual server may perform on a real or virtual device. Providing a secure virtual environment is more important than ever because increasing numbers of organizations and institutions worldwide are turning to virtualization to reduce IT costs. CP takes advantage of this mechanism to limit the scope of some hardware or software failures. When the error is isolated to a particular virtual server, only that virtual server fails and the operation can be retried or the virtual server can be reinitialized (rebooted) without affecting any testing or production work running in other virtual servers. CP is designed so failures that occur in virtual servers don’t affect it or other virtual servers. While hardware support for virtualization now appears in both Intel* and AMD processors, the System z* solution is the only platform that has two levels of hardware virtualization. The server’s LPAR support u s e s t he i nte r pr e t i v e execution facility to create t he pa r t it ion i n wh ic h z/VM runs. LPAR issues a SIE instruction to run the In the simplest terms, z/VM is first-level partition that composed of a virtual-machine hypervisor and the basic software contains CP. Within that instruction stream CP will needed to manage the issue the SIE instruction to environment. The hypervisor, run a second-level virtual called the Control Program (CP), machine. T he hardware takes the principles of CPU and handles both. But if the memory partitioning—which at virtual machine is running the hardware level are implemented within the processor a not her copy of z / V M , the CP running there will and the Processor Resource/ naturally issue a SIE to Systems Manager* (PR/SM*)— r un a third-level guest. and extends them with powerful Because there’s hardware virtualization, sharing or the support for only two levels partitioning of real storage and of SIE, the first-level CP network hardware resources, or intercepts the instruction by emulating their behavior. and simulates it. In most CP maintains a separate cases, this simulation is execution stream for each virtual t he modif ication of t he server. By doing so, CP can inputs to the Level 3 SIE operate without interference or harm, intentional or not, from the instruction to ref lect the second-level system’s view virtual servers it hosts, as well as of the third-level guest. protect the virtual servers from each other. This separation is called system integrity. In order Virtual Memory to maintain this separation, CP Like other platforms, the uses special hardware features to m a i n f r a me pr ov ide s a mediate access to memory, the dynamic address translaCPU and peripheral devices. —A.A. What is z/VM? 34 M AY/J U N E 2 0 0 9 ibms ystemsmag .com/mai nframe

IBM Systems Magazine, Mainframe digital edition - May/June 2009

Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe digital edition - May/June 2009

IBM Systems Magazine, Mainframe digital edition - May/June 2009
Table of Contents
Editor's Desk:  High-Flying Security
Trends:  IBM Cognos 8 BI for Linux on System z Makes Reliable Data Available Anywhere
IT Today:  New System x and BladeCenter Servers Help Your Organization Reach Its Goals
Focus on Storage: Virtual Tape Facility for MainframeJoins IBM Arsenal
Q & A:  Hybrid Technology Takes Supercomputing Beyond Moore’s Law
Case Study:  The City and County of Honolulu Allows Its Applications to Dictate the Platforms on Which They Run
Cover Story:  IBM’s z/VM is a Proven Solution for Today’s IT Environments
Feature:  IBM’s Dynamic Infrastructure Helps Companies Reduce Costs, Manage Risks and Improve Services
Administrator:  DB2 9 Features Help Ensure Compliance
Product News
Advertiser Index
Stop Run:  Barry Merrill’s Accidental DiscoveriesEnhance the Mainframe
Reference Point
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - IBM Systems Magazine, Mainframe digital edition - May/June 2009
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover2
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 1
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Table of Contents
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 3
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 4
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 5
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 6
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 7
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Editor's Desk:  High-Flying Security
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 9
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Trends:  IBM Cognos 8 BI for Linux on System z Makes Reliable Data Available Anywhere
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 11
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 12
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 13
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - IT Today:  New System x and BladeCenter Servers Help Your Organization Reach Its Goals
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 15
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 16
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 17
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 18
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 19
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Focus on Storage: Virtual Tape Facility for MainframeJoins IBM Arsenal
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 21
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 22
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 23
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Q & A:  Hybrid Technology Takes Supercomputing Beyond Moore’s Law
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 25
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 26
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 27
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Case Study:  The City and County of Honolulu Allows Its Applications to Dictate the Platforms on Which They Run
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 29
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 30
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 31
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover Story:  IBM’s z/VM is a Proven Solution for Today’s IT Environments
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 33
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 34
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 35
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 36
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 37
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 38
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 39
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Feature:  IBM’s Dynamic Infrastructure Helps Companies Reduce Costs, Manage Risks and Improve Services
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 41
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 42
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 43
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 44
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 45
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 46
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 47
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Administrator:  DB2 9 Features Help Ensure Compliance
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 49
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 50
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 51
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Product News
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 53
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 54
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Advertiser Index
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Stop Run:  Barry Merrill’s Accidental DiscoveriesEnhance the Mainframe
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover3
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover4
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Reference Point
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - RF2
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